The use in automobiles and other transport vehicles of various braking devices such as drum brake assemblies, disc brake assemblies, and the like is well-known. Such devices function to retard or stop vehicle motion, often from high velocities and at high rates of vehicle deceleration. In the braking process much or very nearly all of the vehicle's kinetic energy is converted to frictional heat at the surfaces of the friction material or materials incorporated in the vehicle braking devices. Such braking process also frequently results in very high operating temperatures being developed in the friction material or materials.
Friction materials incorporated in the known braking devices have generally utilized discrete reinforcement fibers or continuous reinforcement filaments for material reinforcement purposes, and often with a compromise as to one or more of the material's qualities of wear-resistance, developed braking noise, and release of fiber debris. U.S. Pat. No. 3,639,197 issued in the name of Spain, for instance, discloses the use of both continuous carbon filaments and randomly-oriented short carbon fibers as reinforcements in the rotor and stator composites of an aircraft brake assembly.
U.S. Pat. No. 3,759,353 issued in the name of Marin teaches the use of both circumferentially-wound carbon filament and woven carbon filament cloth reinforcements in a disc brake friction disc composite structure.
U.S. Pat. No. 4,278,153 issued in the name of Venkatu discloses a brake disc construction having a copper or copper-plated metal honeycomb core reinforcement that is filled with a powdered friction material, normally comprised of powdered metals and including powdered copper. The powdered friction material is subsequently sintered at an elevated temperature in the range of 1,800 to 2,000 degrees Fahrenheit to form a unitary structure that is made up essentially of single phase, metal-to-metal bonded material resulting from solid state fusion of the mass.
U.S. Pat. No. 4,373,038 issued in the name of Moraw et al. teaches an asbestos-free friction material useful for brake linings, clutches, etc. and comprising a combination of discrete aramide fibers, mineral fibers, and steel fibers reinforcing a hardenable binder.
U.S. Pat. No. 4,384,640 issued in the name of Trainor et al. discloses a friction composition wherein aramid fibers only, sometimes in continuous filament form and sometimes in discrete fiber form, are utilized as reinforcements in the fabrication of various brake or clutch components.
U.S. Pat. No. 4,418,115 issued in the name of Le Lannou teaches a friction lining material for use in brakes, clutches, and other applications having both mineral fibers and organic fibers as reinforcements in a mixture having fillers and a binder. The organic fibers are at least partially composed of a cross-linkable, fusible type such as acrylic or modacrylic fibers.
U.S. Pat. No. 4,997,067 granted in the name of Watts also teaches a friction material for brakes, clutches, etc. wherein the reinforcing medium is a woven fabric that includes fluorine (polytetraf luoroethylene) fibers in yarn form. See also U.S. Pat. No. 3,365,041 granted in the name of Stormfeltz for a friction clutch teaching of the earlier conventional use of both asbestos fibers and glass fibers in a woven reinforcing fabric that is embedded in a friction material composition having also fillers and phenol formaldehyde resin binder.
As to teachings concerning noise reduction in a braking device, see U. S. Pat. No. 5,083,643 issued in the name of Hummel et al. and assigned to the assignee of this invention. The friction material disclosed therein incorporated reinforcement fibers which are more particularly described as being glass fibers, rock wool fibers, processed mineral fibers, or refractory material fibers.
Also, see U.S. Pat. Nos. 3,673,058 and 3,790,654 issued in the names of Jackson et al. and Bagley, respectively, for disclosures of apparatus and methods for manufacturing honeycomb core materials.
Our invention offers performance advantages over the friction materials referenced above, particularly with respect to resonance noise reduction, increased wear resistance, more consistent friction material performance, and minimizing release of fiber debris. Other advantages will become apparent from a careful consideration of the described invention and of the method of friction material fabrication or manufacture that is detailed and claimed.